1. Field of the Invention
The present invention relates to an improvement of a tilt lock device for an outboard boat motor.
2. Description of the Related Art
A prior art tilt lock device for an outboard motor is shown in (1) Japanese Patent Application Publication (JP-B) No. 2-58155 (TILT LOCK DEVICE FOR OUTBOARD MOTOR) and (2) Japanese Patent Application Laid-open (JP-A) No. 4-5195 (TILT CYLINDER DEVICE FOR OUTBOARD MOTOR).
The prior art reference (1) reduces a tilt-up operation force by a simple structure in addition to a basic function of the tilt lock device. As shown in FIGS. 4 and 5 of this publication, this device comprises a cylinder 8, a piston 12 movably inserted in the cylinder 8, a rod 11 as a piston rod mounted to the piston 12, first and second chambers 8a and 8b as oil chambers defined on opposite sides of the piston 12, a communication passage 24 for interconnecting these first and second chambers 8a and 8b with each other outside the cylinder 8 to bypass the piston 12, a switch valve 37 provided in an intermediate portion of the communication passage 24, a tank 45 connected to the switch valve 37, and a gas chamber 38 constituting an operation force device in the tank 45 to compensate the volume in the cylinder 8 with advancing and retreating movement of the rod 11.
The prior art reference (2) discloses a tilt lock device having substantially the same function as the prior art (1), and prevents the outboard body from being damaged when an excessive external force is applied to the outboard body during forward travel or reverse travel in the shallow. As shown in FIG. 3 in this publication, this device comprises a tilt cylinder device 10 including a piston 13 vertically movably inserted in a cylinder 11, a free piston 14 disposed above the piston 13, a piston rod 12 mounted to a lower portion of the piston 13, and a gas chamber 15 disposed above the free piston 14 in the cylinder 11.
In the prior art (1), since the tank 45 and the cylinder 8 are separate members, the tilt lock device occupies a large space. Further, since the communication passage 24 is extended from the cylinder 8 outward, and the tank 45 is further connected to the switch valve 37 provided at an intermediate portion of the communication passage 24, there is a problem with the assembling operation.
In the prior art (2), since the gas chamber 15 is provided at an upper portion in the cylinder 11, the entire length of the cylinder 11 is long and therefore, there is a problem, because the a length required for mounting the tilt cylinder device 10 is long.